Hydraulic transmission



Febc 10 1942, L. M. PERSONS' lHYDRAULIC TRANSMISSION Filed Dec. 27, 1938 Patented Feb. 10, V1942 nYnnAULIC :rnANsivnssioN l Lawrence Persons, St. Louis County, Mo., as-

signor to Automatic Control Corporation, St. Louis, Mo., a corporation of Delaware Application December 27, 193s, serial Nazimso (ci. o- 131) The present invention relates generally to hydraulic transmission mechanisms, and more particularly to a hydraulic transmission mechanism which includes fluid-actuated diaphragms con` nected by a iiuid-illed tube with power means in association with one diaphragm and powerreceiving means in association with the other diaphragm employed as a fail-safe control.

An object of the present invention is to pro- Y vide a novel hydraulic power transmission mechanism.

Another object is to provide a novel hydraulic power transmission mechanism which includes spaced fluid-actuated diaphragms connected by a uid-lled tube with power means associated 4with one diaphragm and power-receiving means associated with the otherdiaphragm.

Another object'is to provide a novel hydraulic transmission mechanism including thermalre sponsive power means which can be subjected to temperaturesv of high degree.

'Another object is to provide a novel control mechanism for furnaces, and the like, which adapted to be fail-safe.

Another object is to provide a control for furnaces, and the like, including aremotelydisposed thermal actuatable power means connected with the power-receiving means by an encased fluid, failures of which are inevitably safe.

Another object is to provide a sturdy and eilicient mechanism of the type described which is adapted to fulfill all of the objects and advantages sought.

y Other objects and, advantages will be apparent y. from the.following, description, taken in conjunction with the accompanying drawing, in which: i j s Y The figure represents a preferred embodiment of a `hydraulic power transmission mechanism constructed in accordance with the teachings of the present invention.

'Referring to the drawing. more particularly by An elongated tube of copper, or other suitable material, has a reduced threaded portion I2 which engages the threaded aperture I0. The end of the tube Il remote from the disc 1 is closed by a member I3 which is-welded or otherwise securely xed in position. The member i3 includes a central threaded aperture |4. A rod I6 of invar, or other suitable materiaLis disposed concentrically of the tube with one end engagingthe depression 6 of the diaphragm S'and the other end .threadedly engaging the threaded aperture |4. The rod |6 has a slot I1 at its free end for adjustment purposes. A lock nut I8 threadedly engages the ,free end of the rod I6 and abuts the member I3. v A tube 20 leads through an opening in the cup "2, preferably ladjacent the juncture of the bottom and the WalLto communicate with the space between the diaphragm 5 and the cup 2. At its other end the tube 20 communicates in similar fashion with a space between the inner face of a cup 2| and the outer face of a diaphragm 22 located within the cup4 2|.l A stud 23 is fixed to the central portion of the diaphragm 22. The cup 2| is secured by screws 24 to` a casing 25 of a switch 26.

The switch 26 is of conventional construction and includes, in addition to the case` 25, a base 21 of insulative material to which the case 25 is connected, and a bisectional switch blade 28 pivoted on a shaft 29 which is secured in opposed walls of the case 25. .The switch blade 26includes an insulativesection 30 and a metallic section 3|v connected by a screw 32. Adjacent the endof the metal section 3| are two conreference numerals, represents a power trans- A mission mechanism constructed in accordance with the conceptsof the present invention.A

A cup 2 of conventional construction includes a central depression 3 and an annular flange 4. Within the cup 2 is a diaphragmv 5'having a vcentral'depression 6, the annular wall ofthe diaphragm beingiixed to the annular wall of the cup to provide a sealed space between Athe outer tacts .33 and 34.V A helical spring 35 biases the lever 28 counterclockwise against the stud 23. A contact is fixed to a bracket 39 which is connected by a screw 40 to the base 21. A contact 40 4|' is fixed to abracket 42 connected by a screw 43 to insulative blocks 44 supported by the' casing 25. Leads 46, 41and'48 are connected to the screws 32, 40, and 113, respectively.

'The lead 48 is in circuit with the'furnacefan 45 and the lead 41 is in circuit with the furnace face o the diaphragm' and the inner face of the cup. A circular disc 1 isr secured to the ilange 4 of the cup 2 by screws 8'. The disc 1 includes a central threaded aperture IIL heat-producing unit. The structural details of the switch 26 may, of course, be varied as desired. for tli'esame per se form no part of the present invention. A'snap-'action switch is very effective.

. Operation TheV present Y transmission mechanism which finds particular adaptation asa furnace, or the like, control, for

it compriseswhat is knownin the trade as a invention is a 'hydraulic power fail-safe device. The tube il and rod i6 are disposed within the bonnet of a furnace to serve as the control and actuating or power means for the switch 2B, performing as a limit switch for the furnace. The switch 26 is disposed beyond the influence of the heat at the furnace bonnet. 'I'he maior portion of the tube 20 together with i its encased fluid are likewise protected from the influence of the heat at the furnace bonnet.

When the temperature surrounding the tube Il and rod I6 reaches a level predetermined as too high, the tube ll will have elongated suiilclently due to the heat to move the rod i6 away from the diaphragm 5. In other words, the tube Il elongates to a greater degree than does the rod IE due to the coefficients of expansion of copper and invar, respectively. As the rod i6 withdraws from the diaphragm downwardly in the drawing, the diaphragm 5 follows due to inherent resiliency, thereby enlarging the space between the diaphragm and the cup. The enlarging of the fluid space permits the spring 35 to pivot the lever 28 counterclockwise to break the burner circuit and to make the fan circuit. The fan functions to cool the furnace.

When the furnace has reached a prec'ietern mined lower temperature, the tube il and the rod I6 will have contracted sufficiently to force the rod i6 into engagement with the diaphragm 5 to diminish the space between the diaphragm 5 and the cup 2. The force exerted 'by the rod i6 is transmitted by the fluid to the stud 23 which pivots the lever 28 clockwise to break the ian circuit and to make the burner circuit. rllhe huid used is a suitable liquid which accurately 'transmits the force applied to the diaphragm 5i to the diaphragm 22.

Should a failure occur in the hydraulic power 'transmission mechanism, as by a rupture oi the tube 20, in which case the :duid would escape, it is clear that the mechanism fails in a safe ren lationship, for, upon the exhaustion oi' iluid within the power'transmission mechanism, the

spring will pivot the lever 28 counterclockwise to make the fan circuit, which will, therefore, function to cool the furnace. The conventional hydraulic thermostat functions contrary to the foregoing, inasmuch as the fluid in the bulbs thereof expands upon the application of heat.

It is apparent that the mechanism disclosed in the drawing and above described fulfills all of the objects and advantages sought therefor. Structural details may, of course, be varied within the scope of the claims.

It is to be understood that the foregoing de scription and accompanying drawing have been given by way of illustration and example and not for purposes of limitation, the invention being limited only by the claims which follow.

What is claimed is:

1. A device adapted to actuate the lever arm of a furnace switch adapted to move between two contacts to alternately close and make a. burner unit circuit and a fan circuit, said actuating deacvamo vice including a thermally actuatable assem blage comprising a rod and tube fixed together at one end, and a hydraulic connecting means comprising spaced diaphragms and a connecting tube, one of said diaphragme being operatively connected to the rod and tube and the other diaphragm being adapted to be operatively connected to the arm of a switch, the connection between the rod and tube and the one diaphragm permitting the application of pressure to the hydraulic connecting means upon cooling of the thermally actuatable assemblage and to release the pressure upon the hydraulic connecting means upon expansion through .heating of the thermally actuatable assemblage, said other diaphragm being adapted to' close the burner unit circuit upon the application of pressure by the thermally actuatable assemblage to 'the hydraulic connecting means, and to permit closing of the fan circuit and breaking of the burner unit circuit upon release of pressure upon the hydraulic connecting means by the thermally actuatable assemblage, thereby providing a fail-safe actuating mechanism.

2. A fail-safe switch comprising a thermally actuatable assemblage including thermally actuatable members and a diaphragm and cup, a second diaphragm and cup spaced from said as semblage, connecting means between the two cups, iiluid within the connecting means and between the cups and diaphragms, a pair of con tacts, a switch member movable between said contacts and operatively connected to the second diaphragm for movement towards one contact, and means urging said member towards the other Contact, said thermally actuatable members being adapted to reduce pressure upon the iirst diaphragm and therethrough on the fluid upon the application thereto of heat to permit the urging means to operate and to apply pressure upon a reduction oi' heat thereto to move the switch member against the urging means, thereby providing a fail-safe operation. 3. A fail-safe switch mechanism including a thermally actuatable assemblage and a hydraulic connecting means operatively engaged therewith, the connection between the thermally actuatable device and the hydraulic connecting means permitting release of pressure upon the latter by the former upon rise in temperature affecting the thermally actuatable assemblage, a two-point furnace switch, one of which points is in the fan circuit and the other of which is in the burner unit circuit, said hydraulic connecting means being connected to the furnace switch to close the burner unit circuit upon positive action upon the hydraulic connecting means by the thermally actuatable assemblage, and to permit breaking of the burner unit circuit and making of the fan circuit upon release of pressure upon the hydraulic connectingmeans by the thermally actuatable assemblage, thereby providing a fail--safe actuating mechanism.

LAWRENCE M. PERSONS. 

